Conditional Statement Error?

Please forgive my experience level, but when I try to run the following
code, I get this error "; error: bad argument type: FILE 24.0". The
"24.0" is the correct answer to the input I give. I have never seen
this error in this format before. The idea behind this code is to
formulate the "Power" when one variable is unknown. Any help is
appreciated.


(defun cower ()
(setq E (GETREAL "Voltage?:"))
(setq I (GETREAL "Amps?:"))
(setq R (GETREAL "Resisitance?:"))

(COND ((= E NIL) (PRINC (RTOS E1 2 3) (SETQ E1 (* (EXPT I 2) R)))) ;;IF
NO VOLTAGE USE THIS FORMULA
((= I NIL) (PRINC (RTOS I1 2 3) (SETQ I1 (/ (EXPT E 2) R))))
;;IF NO AMPERAGE USE THIS FORMULA
((= R NIL) (PRINC (RTOS R1 2 3) (SETQ R1 (* E I)))))
;;IF NO RESISTANCE USE THIS FORMULA
(princ))

 

(SETQ E1 (* (EXPT I 2) R)))) ??? (TYP)

 

Like Mark says: set your variables before trying to (princ) them. I think
this does what you're trying to do:

(defun cower (/ e i r e1 i1 r1)
(setq E (GETREAL "Voltage?:"))
(setq I (GETREAL "Amps?:"))
(setq R (GETREAL "Resisitance?:"))
(COND
((not E)
(SETQ E1 (* (EXPT I 2) R))
(PRINC (RTOS E1 2 3))
)
((not I)
(SETQ I1 (/ (EXPT E 2) R))
(PRINC (RTOS I1 2 3))
)
((not R)
(SETQ R1 (* E I))
(PRINC (RTOS R1 2 3))
)
)
(princ)
)

However, you may want to include some instructions about leaving the unknown
value blank ... the casual user may fill in all three values and, will then
get nothing but a blank Command: prompt in response.
___

 

Thank you very much!